This invention relates to a method of monitoring sterilization residual, such as ethylene oxide sterilization residual, in articles which have been sterilized.
Ethylene oxide sterilization is commonly used in hospitals and the like for treating articles of plastic, paper, rubber or the like which cannot withstand steam sterilization. Typically, it involves humidifying the articles to be sterilized and then contacting them with ethylene oxide usually in admixture with an inert diluent such as dichlorodifluoromethane. Articles subjected to such sterilizing treatment have been found to contain ethylene oxide, ethylene chlorohydrin and ethylene glycol. These residual contaminants are referred to as ethylene oxide sterilization residual.
Ethylene oxide sterilization residual has been recognized as a problem. Articles used upon completion of ethylene oxide sterilization are considered unsafe because of such residual; (see, for example, "Evaluation of Sterilization By Gaseous Ethylene Oxide" by H. Stierli, M.S., et al, Public Health Monograph #68, p. 13, which refers to the severe chemical burns which can result from use of ethylene oxide sterilized rubber gloves which have not been aerated properly). Procedures were developed wherein such articles are quarantined on the shelf until the residual has been sufficiently desorbed, for example, for up to 168 hours. More recently, gas sterilizers have been used with aeration chambers having aeration cycles of, for example, 8-12 hours, to remove residual contaminants. The basic question presented is whether the possibility of biological hazard exists if the articles are put to use within what would be practical times considering hospital inventories.
Chemical analytical techniques can be used to quantitatively measure the various components which sterilization residual comprises and can be of benefit if properly relatable to other biological data. Such analysis has the disadvantage of requiring separate analyses for a number of components.
Also, various methods of toxicity testing for sterilant residues are known: for example, subcutaneous injection, implantation, topical tissue (including ocular) application. oral toxicity and intravenous injection. Such methods are referred to, for example, in the following: Wilson, John E., "Ethylene Oxide Sterilant Residues", Bulletin of the Parenteral Drug Association, 24, 226-234 (1970); Anderson, Shirley R., "Ethylene Oxide Residues in Medical Materials", Bulletin of the Parenteral Drug Association, 27, 49-57 (1973), McDonald, T. O. et al, "Acute Ocular Toxicity of Ethylene Oxide Ethylene Glycol, and Ethylene Chlorohydrin", Bulletin of the Parenteral Drug Association, 27, 153-164 (1973). These test methods are relatively cumbersome; time consuming, costly, and frequently not within the capability of certain laboratories especially hospital laboratories.
It is a primary objective of the present invention to provide a biological method for indicating possible biological hazard due to sterilization residual in an article, which method is practical in application and directly relatable to the end answer sought by such testing, i.e., safety for use.